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127 lines
3.0 KiB
C
127 lines
3.0 KiB
C
/*
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* Utility used to calculate the 6rd subnet.
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*
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* Copyright 2012, Stéphan Kochen <stephan@kochen.nl>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/errno.h>
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#include <arpa/inet.h>
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#include <netinet/in.h>
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#define INET_PREFIXSTRLEN (INET_ADDRSTRLEN+3)
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#define INET6_PREFIXSTRLEN (INET6_ADDRSTRLEN+4)
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static void print_usage()
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{
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fprintf(stderr, "Usage: 6rdcalc <v6 prefix>/<mask> <v4 address>/<mask>\n");
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exit(1);
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}
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static void print_error()
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{
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fprintf(stderr, "%s", strerror(errno));
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exit(1);
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}
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static void parse_str(int af, char *str, void *addr, unsigned long *mask)
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{
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int ret;
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char *slash;
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/* Split the address at the slash. */
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if ((slash = strchr(str, '/')) == NULL)
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print_usage();
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*slash = '\0';
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/* Parse the address. */
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if ((ret = inet_pton(af, str, addr)) != 1) {
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if (ret == 0)
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print_usage();
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else
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print_error();
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}
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/* Parse the mask. */
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*mask = strtoul(slash+1, NULL, 10);
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if ((af == AF_INET && *mask > 32) ||
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(af == AF_INET6 && *mask > 128))
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print_usage();
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}
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int main(int argc, const char **argv)
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{
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char v6str[INET6_PREFIXSTRLEN], v4str[INET_PREFIXSTRLEN];
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struct in6_addr v6;
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struct in_addr v4;
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unsigned long v6it, v4it, mask;
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unsigned char *byte4, *byte6;
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unsigned char bit4, bit6;
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/* Check parameters. */
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if (argc != 3)
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print_usage();
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/* Parse the v6 address. */
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strncpy(v6str, argv[1], INET6_PREFIXSTRLEN);
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v6str[INET6_PREFIXSTRLEN-1] = '\0';
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parse_str(AF_INET6, v6str, &v6, &v6it);
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/* Parse the v4 address */
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strncpy(v4str, argv[2], INET_PREFIXSTRLEN);
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v6str[INET_PREFIXSTRLEN-1] = '\0';
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parse_str(AF_INET, v4str, &v4, &v4it);
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/* Check if the combined mask is within bounds. */
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mask = (32 - v4it) + v6it;
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if (mask > 128)
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print_usage();
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/* Combine the addresses. */
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while (v4it < 32) {
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byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 3);
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byte4 = (unsigned char *)(&v4.s_addr) + (v4it >> 3);
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bit6 = 128 >> (v6it & 0x07);
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bit4 = 128 >> (v4it & 0x07);
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if (*byte4 & bit4)
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*byte6 |= bit6;
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else
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*byte6 &= ~bit6;
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v4it++; v6it++;
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}
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/* Clear remaining bits. */
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while (v6it < 128) {
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byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 2);
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bit6 = 128 >> (v6it & 0x07);
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*byte6 &= ~bit6;
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v6it++;
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}
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/* Print the subnet prefix. */
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if (inet_ntop(AF_INET6, &v6, v6str, sizeof(v6str)) == NULL)
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print_error();
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printf("%s/%lu\n", v6str, mask);
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return 0;
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}
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